Catching Message Handling Exceptions with the #Exceptionhandler - axon

Question

I have two application e.g) A, B
A has a Saga
B is just web application
A sent Command messages to B and
B sent exception for that Command to A's Saga and A's Saga received well
and B have a #ExceptionHandler which I hope to be invoked but it's not working
How can I make them be invoked?
EDIT
this is A application's Saga that sends command messages to B application
and deals with exception which B sent
#Saga
public class OrderSaga {
#Autowired
private transient CommandGateway commandGateway;
#StartSaga
#SagaEventHandler(associationProperty = "orderId")
public void handle(CreateOrderEvent evt) {
String paymentId = UUID.randomUUID().toString();
SagaLifecycle.associateWith("paymentId", paymentId);
commandGateway.send(new CreatedPaymentCommand(paymentId, evt.getUserId(),evt.getFoodPrice())).exceptionally(exp -> {
System.out.println("got it");
System.out.println(exp.getMessage());
return null;
});
}
}
this is B application that throws exception for test
#Aggregate
#NoArgsConstructor
public class PaymentAggregate {
#AggregateIdentifier
private String paymentId;
private String userId;
private PaymentStatus status;
#CommandHandler
public PaymentAggregate(CreatedPaymentCommand cmd) {
throw new IllegalStateException("this exception was came from payment aggregates");
// AggregateLifecycle.apply(new CreatedPaymentEvent(cmd.getPaymentId(),
// cmd.getUserId(),cmd.getMoney()));
}
#ExceptionHandler(resultType = IllegalStateException.class)
public void error(IllegalStateException exp) {
System.out.println(exp.getMessage());
}
// I want this #ExceptionHandler to be invoked
#EventSourcingHandler
public void on(CreatedPaymentEvent evt) {
this.paymentId = evt.getPaymentId();
this.userId = evt.getUserId();
}
}
A application catch exception well like below
2021-08-24 11:46:43.534 WARN 14244 --- [ault-executor-2] o.a.c.gateway.DefaultCommandGateway : Command 'com.common.cmd.CreatedPaymentCommand' resulted in org.axonframework.commandhandling.CommandExecutionException(this exception was came from payment aggregates)
got it
this exception was came from payment aggregates
but B is not I thought that B's #ExceptionHandler will catch that exception
in short, How can I make B's #ExceptionHandler to be invoked

Answer 1

It doesn't work right now because the exception is thrown from the constructor of your aggregate.
As you are using a constructor command handler, there is no instance present yet.
And without an instance, Axon Framework cannot spot the #ExceptionHandler annotated method you've set up.
This is the only missing point for the exception handlers at this stage. Honestly, the reference guide should be a bit more specific about this. I am sure this will change in the future, though.
There's a different approach for having a command handler that constructs the aggregate and that can use the #ExceptionHandler: with the #CreationPolicy annotation. The reference guide has this to say about it, by the way.
Thus, instead of having a constructor command handler, you would set up a regular command handler using the AggregateCreationPolicy.ALWAYS.
That would adjust your sample like so:
#Aggregate
#NoArgsConstructor
public class PaymentAggregate {
#AggregateIdentifier
private String paymentId;
private String userId;
private PaymentStatus status;
#CommandHandler
#CreationPolicy(AggregateCreationPolicy.ALWAYS)
public void handle(CreatedPaymentCommand cmd) {
throw new IllegalStateException("this exception was came from payment aggregates");
// AggregateLifecycle.apply(new CreatedPaymentEvent(cmd.getPaymentId(),
// cmd.getUserId(),cmd.getMoney()));
}
#ExceptionHandler(resultType = IllegalStateException.class)
public void error(IllegalStateException exp) {
System.out.println(exp.getMessage());
}
// I want this #ExceptionHandler to be invoked
#EventSourcingHandler
public void on(CreatedPaymentEvent evt) {
this.paymentId = evt.getPaymentId();
this.userId = evt.getUserId();
}
}
Please give this a try in your application, #YongD.